The present invention relates to a heat-resisting material, and particularly, to a heat-resisting material used as a heat-insulating material or a joint packing for high-temperature furnaces and high-temperature ducts, having high heat resistance and restoring property as well as an excellent workability.
Heat-resisting materials are commonly used as heat-insulating material or joint packing on the wall surfaces or at the joints of the high-temperature furnaces, high-temperature ducts and like equipment. Various types of heat-resisting material, such as those comprising amassed alumina-based or alumina-silica-based ceramic fibers and those produced by adding an expansive material such as vermiculite to the ceramic fibers, have been proposed.
For example, Japanese Patent Publication (KOKOKU) No. 7-115962 discloses a composite heat-insulating material (composite heat-resisting material) comprising a heat-expansive core composed of sepiolite, vermiculite, ceramic fiber and an organic binder and a heat-insulating material (sheathing material) comprising alumina-based or alumina-silica-based ceramic fibers, the core being partially or entirely sheathed with the heat-insulating material. Such a composite heat-insulating material can make up for the heat shrinkage of ceramic fibers by virtue of expansion of the heat-expansive core, so that there has no risk of causing formation of spaces or cracks when used at the joints of high-temperature furnaces or such equipment.
This heat-resisting material of Japanese Patent Publication (KOKOKU) No. 7-115962, however, involves the problem that the expansive material used therein is susceptible to heat deterioration with shrinkage of the fibers under placed under a high-temperature condition of not less than 600.degree. C., so that when the heat-resisting material is applied to the boundaries between the blocks of the same heat-resisting material or the joints of equipment, there may be formed openings or spaces at such portion, or the applied heat-resisting material itself may be cracked, causing a reduction of its heat-insulating effect and/or sealing effect. Further, in case of applying the heat-resisting material to the boundaries between blocks thereof or joints thereof in expectation of the possible contraction percentage of the fibers in use under a high-temperature condition, there is required volumetrically massive compression molding, which gives rise to the problems in working of the material.
As a results of the earnest studies, it has been found that by the combination of a fiber aggregate as a core material, comprising specific crystalline alumina short fibers having excellent heat resistance, and a sheathing for maintaining the initial shape of the core fiber aggregate, the above-mentioned problems have been solved. On the basis of the finding, the present invention has been attained.
Further, this composite heat-insulating material is unsatisfactory in expansion percentage as a whole. Also, since the quality of the composite heat-insulating material mostly depends on the heat resisting properties of the heat-expansive material constituting the core, such composite heat-insulating material is unsuitable in use at high temperatures of not less than 800.degree. C.